The present invention relates to a combination exhaust gas post treatment/muffler device in the exhaust gas section of an internal combustion engine, especially a diesel engine of a commercial vehicle, such as a truck or bus, and including a muffler that is spatially delimited by a front and rear end wall as well as a peripheral outer wall, and in the interior of which is built in at least one preliminary oxidation catalytic converter, which significantly increases the NO2 amount in the exhaust gas that is flowing through, and at least one exhaust gas post treatment device, whereby exhaust gas that is to undergo post treatment can be introduced into the muffler via an inlet tube, and after flowing through the preliminary oxidation catalytic converter as well as the exhaust gas post treatment device can again be conveyed out of the muffler in a cleaned and indirectly muffled state.
Combination exhaust gas post treatment/muffler devices of the aforementioned type have been disclosed, for example, in the 23rd International Viennese Motor Symposium on the 25th and 26th of Apr. 2002 and have been documented in the Progress Reports, VDI series 12 Nr. 490, volume 2, Düsseldorf, VDI publication 2002, pages 196-216. In this connection, a system was introduced where four exhaust gas post treatment modules were disposed in a muffler for parallel flow therethrough, whereby each module, enclosed in a casing, is provided with a circular cylindrical preliminary oxidation catalytic converter and, following immediately coaxially a circular cylindrical particle separator having the same diameter.
Due to the use of sulfur-containing fuels, there results during the oxidation of the exhaust gas sulfuric acid that has a very corrosive effect within the exhaust gas post treatment/muffling system. This formation of corrosion caused by sulfuric acid is counteracted by the use of high-quality austenitic stainless steel materials during the manufacture of the exhaust gas post treatment and muffling devices. However, in comparison to structural steels these austenitic stainless steels are much more expensive, and require for the processing of appropriate semi-finished articles, such as sheets or plates, also considerably more complicated and expensive tools, which on the whole thus cause relatively high manufacturing costs for such systems that are resistant to sulfuric acid. In comparison to exhaust gas post treatment/muffling systems that require no configuration that is resistant to sulfuric acid, the system costs for an embodiment that is resistant to sulfuric acid increases by a factor of 3 to 5.
It is therefore an object of the present invention to provide exhaust gas post treatment/muffling devices of the aforementioned general type with structural features that provide the possibility of remedying the problem of corrosion caused by sulfuric acid in a cost-reducing manner.